The substrate for electronic devices such as a substrate for displays has been conventionally formed of glass because of good gas-barrier property and heat resistance thereof. In recent years, earnest studies on flexible displays produced from a plastic film have been made since the plastic film has excellent properties such as light weight, unbreakableness and excellent processability. However, the plastic film is readily susceptible to penetration of gases such as water vapor and suffers from drawbacks such as insufficient heat resistance, etc., as compared to glass, and therefore has many problems upon practical use.
To solve these problems, Patent Document 1 discloses a gas-barrier film with a laminated structure including a silicon oxide layer formed on a transparent polymer film by a plasma chemical vapor deposition method, and another silicon oxide layer obtained by coating a polysilazane-containing solution thereon and then heat-treating the coated solution. However, in order to form a film of an inorganic compound by the plasma chemical vapor deposition method, the use of a large size vacuum apparatus is needed, and there also tends to arise such a problem that the costs for production of the film are hardly reduced owing to a low production rate thereof.
Patent Document 2 discloses a gas-barrier film including a base material, and a barrier layer formed on at least one surface of the base material by subjecting a polysilazane film to plasma treatment. However, in the method, the use of an apparatus for the plasma treatment is inevitably needed, and the method further has such as a problem that the resulting film is considerably deteriorated in barrier property after the heat-treatment step depending upon a kind of base material used.
Patent Document 3 discloses a process for producing a flexible gas-barrier film which includes the steps of coating a polymer having a silazane skeleton as a base unit on a resin substrate and irradiating vacuum ultraviolet rays to the coated polymer to laminate a film of the polymer on the resin substrate. However, the process of Patent Document 3 needs a facility for irradiating vacuum ultraviolet rays and further has such a problem that a large number of laminating steps are required for laminating the polymer film.